This invention pertains to the art of manufacturing thin-walled honeycomb structures from extrudable material such as ceramic pastes, molten glasses, plastics, molten metals, and similar materials which have the property of being able to flow or plastically deform during extrusion while being able to become sufficiently rigid immediately thereafter so as to maintain structural and dimensional integrity. In one aspect the present invention relates to an improved extrusion die structure and method for forming uniform thin-walled cellular or honeycomb type articles having a plurality of openings or passages extending therethrough with wall portions between such openings having a preferred thickness of between about 0.005 inches and 0.10 inches, so as to provide open frontal areas of about 75% or greater. In another aspect the present invention relates to a method for making the aforesaid die.
U.S. Pat. No. 3,790,654 shows an extrusion die made in two basic steps. First, a gridwork of discharge slots is cut into the outlet face. This operation forms core pins. Second, feed holes are drilled into the inlet face to register with alternate intersections of the gridwork. There is no secondary gridwork.
U.S. Pat. No. 1,601,536 shows two sets of grids in the die face, one for air, one for candy. Air enters the air slots from the atmosphere, and the air grid has no contact with the candy feed grid, whether within the grid or outside.
U.S. Pat. No. 3,406,435 shows spaced pins (or sleeves) attached to the face of an extrusion die. Spaces between the pins form the walls of the honeycomb. There is no secondary grid.
U.S. Pat. No. 3,824,196 shows a die with "primary" and "secondary" channels. However, "primary" refers simply to feed holes and "secondary" to a single grid. There is no second grid laid down between the slots of a first grid. The die offers basically two-step flow action, with no secondary grid such as is in the instant invention.
U.S. Pat. No. 4,298,328 discloses a masking spacer for a die perimeter, so as to minimize distortion of peripheral cells of an extruded honeycomb structure.